more comments, sync check

Signed-off-by: Alex Chi <iskyzh@gmail.com>

mini-lsm/src/block/builder.rs

@@ -2,15 +2,18 @@ use bytes::BufMut;
 
 use super::{Block, SIZEOF_U16};
 
-/// Builds a block
+/// Builds a block.
 pub struct BlockBuilder {
+    /// Offsets of each key-value entries.
     offsets: Vec<u16>,
+    /// All key-value pairs in the block.
     data: Vec<u8>,
+    /// The expected block size.
     block_size: usize,
 }
 
 impl BlockBuilder {
-    /// Creates a new block builder
+    /// Creates a new block builder.
     pub fn new(block_size: usize) -> Self {
         Self {
             offsets: Vec::new(),
@@ -23,7 +26,7 @@ impl BlockBuilder {
         self.offsets.len() * SIZEOF_U16 + self.data.len() + SIZEOF_U16
     }
 
-    /// Adds a key-value pair to the block
+    /// Adds a key-value pair to the block. Returns false when the block is full.
     #[must_use]
     pub fn add(&mut self, key: &[u8], value: &[u8]) -> bool {
         assert!(!key.is_empty(), "key must not be empty");
@@ -41,11 +44,12 @@ impl BlockBuilder {
         true
     }
 
+    /// Check if there is no key-value pair in the block.
     pub fn is_empty(&self) -> bool {
         self.offsets.is_empty()
     }
 
-    /// Builds a block
+    /// Finalize the block.
     pub fn build(self) -> Block {
         if self.is_empty() {
             panic!("block should not be empty");

mini-lsm/src/block/iterator.rs

@@ -4,6 +4,7 @@ use bytes::Buf;
 
 use super::Block;
 
+/// Iterates on a block.
 pub struct BlockIterator {
     block: Arc<Block>,
     key: Vec<u8>,
@@ -21,45 +22,44 @@ impl BlockIterator {
         }
     }
 
+    /// Creates a block iterator and seek to the first entry.
     pub fn create_and_seek_to_first(block: Arc<Block>) -> Self {
         let mut iter = Self::new(block);
         iter.seek_to_first();
         iter
     }
 
+    /// Creates a block iterator and seek to the first key that >= `key`.
     pub fn create_and_seek_to_key(block: Arc<Block>, key: &[u8]) -> Self {
         let mut iter = Self::new(block);
         iter.seek_to_key(key);
         iter
     }
 
+    /// Returns the key of the current entry.
     pub fn key(&self) -> &[u8] {
         debug_assert!(!self.key.is_empty(), "invalid iterator");
         &self.key
     }
 
+    /// Returns the value of the current entry.
     pub fn value(&self) -> &[u8] {
         debug_assert!(!self.key.is_empty(), "invalid iterator");
         &self.value
     }
 
+    /// Returns true if the iterator is valid.
     pub fn is_valid(&self) -> bool {
         !self.key.is_empty()
     }
 
+    /// Seeks to the first key in the block.
     pub fn seek_to_first(&mut self) {
         self.seek_to(0);
     }
 
-    pub fn len(&self) -> usize {
-        self.block.offsets.len()
-    }
-
-    pub fn is_empty(&self) -> bool {
-        self.block.offsets.is_empty()
-    }
-
-    pub fn seek_to(&mut self, idx: usize) {
+    /// Seeks to the idx-th key in the block.
+    fn seek_to(&mut self, idx: usize) {
         if idx >= self.block.offsets.len() {
             self.key.clear();
             self.value.clear();
@@ -70,6 +70,7 @@ impl BlockIterator {
         self.idx = idx;
     }
 
+    /// Move to the next key in the block.
     pub fn next(&mut self) {
         self.idx += 1;
         self.seek_to(self.idx);
@@ -89,6 +90,7 @@ impl BlockIterator {
         self.value.extend(value);
     }
 
+    /// Seek to the first key that >= `key`.
     pub fn seek_to_key(&mut self, key: &[u8]) {
         let mut low = 0;
         let mut high = self.block.offsets.len();

mini-lsm/src/lib.rs

@@ -1,2 +1,3 @@
 pub mod block;
+pub mod storage;
 pub mod table;

mini-lsm/src/storage.rs

@@ -0,0 +1 @@
+pub struct Storage {}

mini-lsm/src/table.rs

@@ -12,11 +12,14 @@ use anyhow::Result;
 
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct BlockMeta {
+    /// Offset of this data block.
     pub offset: usize,
+    /// The first key of the data block.
     pub first_key: Bytes,
 }
 
 impl BlockMeta {
+    /// Encode block meta to a buffer.
     pub fn encode_block_meta(block_meta: &[BlockMeta], buf: &mut Vec<u8>) {
         let mut estimated_size = 0;
         for meta in block_meta {
@@ -34,6 +37,7 @@ impl BlockMeta {
         assert_eq!(estimated_size, buf.len() - original_len);
     }
 
+    /// Decode block meta from a buffer.
     pub fn decode_block_meta(mut buf: impl Buf) -> Vec<BlockMeta> {
         let mut block_meta = Vec::new();
         while buf.has_remaining() {
@@ -46,6 +50,7 @@ impl BlockMeta {
     }
 }
 
+/// A file object.
 pub struct FileObject(Bytes);
 
 impl FileObject {
@@ -73,6 +78,7 @@ pub struct SsTable {
 }
 
 impl SsTable {
+    /// Open SSTable from a file.
     pub fn open(file: FileObject) -> Result<Self> {
         let len = file.size();
         let raw_meta_offset = file.read(len - 4, 4)?;
@@ -85,7 +91,8 @@ impl SsTable {
         })
     }
 
-    fn read_block(&self, block_idx: usize) -> Result<Arc<Block>> {
+    /// Read a block from the disk.
+    pub fn read_block(&self, block_idx: usize) -> Result<Arc<Block>> {
         let offset = self.block_metas[block_idx].offset;
         let offset_end = self
             .block_metas
@@ -98,13 +105,15 @@ impl SsTable {
         Ok(Arc::new(Block::decode(&block_data[..])))
     }
 
-    fn find_block_idx(&self, key: &[u8]) -> usize {
+    /// Find the block that may contain `key`.
+    pub fn find_block_idx(&self, key: &[u8]) -> usize {
         self.block_metas
             .partition_point(|meta| meta.first_key <= key)
             .saturating_sub(1)
     }
 
-    fn num_of_blocks(&self) -> usize {
+    /// Get number of data blocks.
+    pub fn num_of_blocks(&self) -> usize {
         self.block_metas.len()
     }
 }

mini-lsm/src/table/builder.rs

@@ -5,6 +5,7 @@ use std::path::Path;
 use super::{BlockMeta, FileObject, SsTable};
 use crate::block::BlockBuilder;
 
+/// Builds an SSTable from key-value pairs.
 pub struct SsTableBuilder {
     builder: BlockBuilder,
     first_key: Vec<u8>,
@@ -15,6 +16,7 @@ pub struct SsTableBuilder {
 }
 
 impl SsTableBuilder {
+    /// Create a builder based on target SST size and target block size.
     pub fn new(target_size: usize, block_size: usize) -> Self {
         Self {
             data: Vec::new(),
@@ -26,6 +28,7 @@ impl SsTableBuilder {
         }
     }
 
+    /// Adds a key-value pair to SSTable, return false when SST full.
     #[must_use]
     pub fn add(&mut self, key: &[u8], value: &[u8]) -> bool {
         if self.data.len() > self.target_size {
@@ -59,6 +62,7 @@ impl SsTableBuilder {
         self.data.extend(encoded_block);
     }
 
+    /// Builds the SSTable and writes it to the given path. No need to actually write to disk until chapter 4 block cache.
     pub fn build(mut self, path: impl AsRef<Path>) -> Result<SsTable> {
         self.finish_block();
         let mut buf = self.data;

mini-lsm/src/table/iterator.rs

@@ -4,6 +4,7 @@ use std::sync::Arc;
 use super::SsTable;
 use crate::block::BlockIterator;
 
+/// An iterator over the contents of an SSTable.
 pub struct SsTableIterator {
     table: Arc<SsTable>,
     blk_iter: BlockIterator,
@@ -18,6 +19,7 @@ impl SsTableIterator {
         ))
     }
 
+    /// Create a new iterator and seek to the first key-value pair.
     pub fn create_and_seek_to_first(table: Arc<SsTable>) -> Result<Self> {
         let (blk_idx, blk_iter) = Self::seek_to_first_inner(&table)?;
         let iter = Self {
@@ -28,6 +30,7 @@ impl SsTableIterator {
         Ok(iter)
     }
 
+    /// Seek to the first key-value pair.
     pub fn seek_to_first(&mut self) -> Result<()> {
         let (blk_idx, blk_iter) = Self::seek_to_first_inner(&self.table)?;
         self.blk_idx = blk_idx;
@@ -47,6 +50,7 @@ impl SsTableIterator {
         Ok((blk_idx, blk_iter))
     }
 
+    /// Create a new iterator and seek to the first key-value pair which >= `key`.
     pub fn create_and_seek_to_key(table: Arc<SsTable>, key: &[u8]) -> Result<Self> {
         let (blk_idx, blk_iter) = Self::seek_to_key_inner(&table, key)?;
         let iter = Self {
@@ -57,6 +61,7 @@ impl SsTableIterator {
         Ok(iter)
     }
 
+    /// Seek to the first key-value pair which >= `key`.
     pub fn seek_to_key(&mut self, key: &[u8]) -> Result<()> {
         let (blk_idx, blk_iter) = Self::seek_to_key_inner(&self.table, key)?;
         self.blk_iter = blk_iter;
@@ -64,18 +69,22 @@ impl SsTableIterator {
         Ok(())
     }
 
+    /// Get the current key.
     pub fn key(&self) -> &[u8] {
         self.blk_iter.key()
     }
 
+    /// Get the current value.
     pub fn value(&self) -> &[u8] {
         self.blk_iter.value()
     }
 
+    /// Check if the iterator is valid.
     pub fn is_valid(&self) -> bool {
         self.blk_iter.is_valid()
     }
 
+    /// Move to the next key-value pair.
     #[allow(clippy::should_implement_trait)]
     pub fn next(&mut self) -> Result<()> {
         self.blk_iter.next();